Charles Oliveira made a narrow escape from the first round against Michael Chandler at UFC 262 before ending things in a hurry in the second.
Oliveira (31-8) dropped Chandler with his first punch after the break and won by TKO 19 seconds into the second round to claim the UFC lightweight title in Houston.
In his 28th UFC fight, the Brazilian earned his first strap, a belt left vacant when the unbeaten Khabib Nurmagomedov decided to retire.
Chandler (22-6) had won the first round 10-8 on two judges' scorecards and 10-9 on the other, but he could not put Oliveira away.
Once the 31-year-old had a chance to compose himself, he showed his class with a single shot.
It was Oliveira's 17th career finish, moving him past Donald Cerrone for the most in UFC history.
In the co-headlining bout, Beneil Dariush dominated Tony Ferguson to win unanimous decision.
The defeat was the third in a row for Ferguson (25-5), the former UFC lightweight interim champion, who previously lost by unanimous decision to Oliveira at UFC 256 in December.
The Iran-born Dariush (21-4-1) said his seventh consecutive win should put him in the conversation in the lightweight ranks, but he plans to take the next several months off as his daughter is due to be born in June.
Also on the card, Rogerio Bontorin defeated Matt Schnell and Katlyn Chookagian beat Viviane Araujo, both by unanimous decision, while Edson Barboza knocked out Shane Burgos at 1:16 in the third round.
For the second time in as many UFC events, an undercard fight ended with an apparent broken limb.
Brazilian veteran Jacare seemed to break his arm in losing by technical submission to Andre Muniz at 3:59 in Round 1. It was the first loss by submission for the 41-year-old Jacare (26-10).
At UFC 261 a fortnight earlier, Chris Weidman broke his leg landing a kick on Uriah Hall.